Simulations of low-conductivity metallic coatings to mitigate instabilities in liner implosions

The MagLIF platform uses a metallic tube or “liner” to compress pre-heated, pre-magnetized fusion fuel, achieving thermonuclear neutron production. However, the liner is distorted by the Joule heating-driven electrothermal instability (ETI), and during implosion, these perturbations further amplify through the magneto Rayleigh-Taylor instability (MRTI), resulting in reduced fusion yield. Previous experiments demonstrate that ETI-stable dielectric coatings can tamp ETI-induced explosions in the underlying metal and reduce ensuing MRTI development. However, modeling the dielectric breakdown process is beyond the scope of commonly used magnetohydrodynamic (MHD) codes, creating uncertainty in simulation predictive capability. An alternative to a dielectric coating is a metallic coating with low electrical conductivity; such a coating can also reduce ETI in the underlying metal while being more straightforward to model in MHD codes. In this presentation, we will use the MHD code ALEGRA to illustrate the tradeoffs of metallic coatings as an option for stabilizing liner implosions. Results of a recent experiment on the Z machine will be presented in the companion talk.